DESCRIPTION The fruit fly Drosophila has many advantages as a model system for testing genotoxic effects of chemicals in vivo, but it differs from humans in its capacity to activate potentially genotoxic xenobiotics. The applicant proposes to produce transgenic flies expressing human cytochrome P450 genes. The expression of human P450 cDNA in transgenic flies will be driven by a constitutive Drosophila P450 gene promoter that is expected to express human P450 protein in high amounts. The first human P450 gene to be tested will be CYP2E1, which activates N-nitrosodimethylemine, a pro-carcinogenic compound that tests positive in classical Drosophila assays and will therefore serve as a positive control. The second human P450 gene will be CYP1A1, which is known to activate polycyclic aromatic hydrocarbons. This research would contribute to the development of new short-term in vivo assays for the detection of potential human carcinogens.